let _Vue = null;
export default class VueRouter {
  static install(Vue) {
    // 判断当前插件是否已经安装
    if (VueRouter.install.installed) {
      return;
    }
    VueRouter.install.installed = true;
    // 把vue构造函数记录到全局变量
    _Vue = Vue;
    // 把创建vue实例时候传入的router对象注册到所有vue实例上
    // 混入

    _Vue.mixin({
      beforeCreate() {
        // 只有构造函数执行一次
        if (this.$options.router) {
          _Vue.prototype.$router = this.$options.router;

          this.$options.router.init();
        }
      }
    });
  }

  constructor(options) {
    this.options = options;
    this.routeMap = {};
    this.data = _Vue?.observable({
      current: "/"
    });
  }

  init() {
    this.createRouteMap();
    this.initComponents(_Vue);
    this.initEvent();
  }

  createRouteMap() {
    // 遍历所有的路由规则，把路由规则解析成键值对的形式，存储到routeMap中
    this.options.routes.forEach(route => {
      this.routeMap[route.path] = route.component;
    });
  }

  initComponents(Vue) {
    Vue.component("router-link", {
      props: {
        to: String
      },
      render(h) {
        return h(
          "a",
          {
            attrs: {
              href: "#" + this.to
            },
            on: {
              click: this.handleClick
            }
          },
          [this.$slots.default]
        );
      },
      methods: {
        handleClick(e) {
          console.log(this.to);
          this.$router.data.current = this.to;
          window.location.hash = "#" + this.to;
          e.preventDefault();
        }
      }
      // template: '<a :href="to"><slot></slot></a>'
    });

    const self = this;
    Vue.component("router-view", {
      render(h) {
        const component = self.routeMap[self.data.current];
        // console.log(self.routeMap);
        return h(component);
      }
    });
  }

  initEvent() {
    window.addEventListener("hashchange", () => {
      this.data.current = window.location.hash.substr(1);
    });
  }
}
